Botulinum toxin acts at the junction between the nerve and muscle. It prevents the release of acetylcholine, the neurotransmitter responsible for signalling the muscle to contract.Once signalling is reduced, the targeted muscle contracts with less force. This reduces repetitive folding of the skin over that muscle.

Because the skin is no longer being repeatedly creased as strongly, expression lines become less pronounced and the overlying skin appears smoother. Dynamic lines generally respond better than established static wrinkles.Treatment can also rebalance facial muscle activity. By selectively reducing activity in specific muscles, it can be used for concerns such as masseter hypertrophy, chin dimpling, gummy smile, downturned mouth corners and platysmal neck bands.

Muscle relaxation begins over the first several days. The full effect is generally assessed at around two weeks, with effects commonly lasting approximately 3–4 months, although duration varies between individuals and treatment areas.